In recent years, there have been concerns about exhaustion of fossil resources typified by petroleum, with mass consumption of the fossil resources. In addition, it is pointed out that global warming is caused by a large amount of carbon dioxide generated with the mass consumption of the fossil resources. Currently, petroleum-based resins are used for a variety of products. In view of the above concerns, however, there is a world-wide boom in using plant-based resins such as polylactic acid-based resins in place of petroleum-based resins.
Polylactic acid is made from a plant such as corn, and is decomposed into water and carbon dioxide by microorganisms in the ground after disposal. In addition, water and carbon dioxide are generated when polylactic acid is incinerated. The carbon dioxide thus generated is absorbed into a plant by photosynthesis, and is used for growth of the plant. In this way, plant-based resins such as polylactic acid-based resins are eco-friendly and recycling materials.
In recent years, a proposal has been made to use plant-based resins such as polylactic acid-based resins for a housing of an electronic device such as a notebook personal computer (PC) and a mobile phone (for example, Japanese Laid-open Patent Publication No. 2001-244645). Although having high rigidity such as bending strength, plant-based resins such as polylactic acid-based resins generally have insufficient impact resistance such as Izod impact strength, and have low heat resistance such as heat deflection temperature. For this reason, it is difficult to use a housing of an electronic device by using a plant-based resin alone. To address this issue, a study has been conducted to form a housing of an electronic device by using a resin made of a mixture of plant-based and petroleum-based resins (for example, Japanese Laid-open Patent Publication No. 2006-182994).
Additionally, as a member using a plant material, there is known a wooden board (also referred to as a particle board) (for example, Japanese Patent No. 2888153 and Japanese Patent No. 2580522). The wooden board is a board obtained in such a manner that crushed lumber, thin paper-like lumber, waste paper or the like (hereinafter referred to as a “fractured material or the like”) are impregnated with an adhesive (a binder), and then are compressed and laminated with each other. The wooden board has characteristics of being relatively hard and rigid. However, a petroleum-based adhesive or solvent is used for the wooden board, and constitutes more than 30% of the wooden board in some cases. In addition, the wooden board is unsuitable for precision processing because a fractured material or the like as a raw material has a great variation in size. Moreover, flame retardancy as specified in UL standards is required for a housing of an electronic device such as a notebook personal computer. For this reason, it is difficult to use a wooden board as it is for a housing of an electronic device.